Various embodiments provide a light guide arrangement for a mobile communications device, a protective sleeve with a light guide arrangement for a cellular telephone, a communications system with a mobile communications device and a method, by means of which the data transmission via an optical path between a mobile communications device and a remote station is improved
Wireless communication is ubiquitous and the need for mobile data links with a high speed is ever increasing. The frequency spectrum for radio-based wireless communication is developing into a rare resource. Therefore, radio-based communications technologies can be complemented or even replaced in the near future by optical wireless communication (OWC). In optical wireless communication, light is used as a medium for the data transmission. Visible light (visible light communication, VLC), infrared (IR), near infrared (NIR) or other wavelengths can be used for the transmission.
Smartglasses for presenting an augmented reality (AR) and video glasses for presenting a virtual reality (VR) are becoming ever more popular. These devices are becoming consumer products. The market is growing and a high market volume is predicted. To this end, low costs are sought after. Depending on the application, smartglasses/video glasses require an extremely high data rate, a low latency time and a bidirectional data link, for example for a videoconference in real time with a high quality. On account of the peculiarities of smartglasses or video glasses, the data link is ideally wireless. Current radio-based technologies are not yet able to provide such connectivity.
Like smartglasses/video glasses, cellular telephones, organizers and other portable devices are also becoming increasingly popular. Depending on the case of application, it may be important to provide a wireless link without producing electromagnetic interference (EMI) in the process. By way of example, this is of interest for use in hospitals, airplanes or other EMI-sensitive regions.
At the same time, the light-based transmission is insensitive to EMI. By way of example, this is of interest for use in industrial surroundings, where radio connections can be disturbed by, for instance, electric motors, strong magnetic fields and electric welding work.
Light cannot penetrate obstacles such as walls and doors, or can only penetrate these with great difficulties. This property can be exploited to provide wireless communications technology in a local and interception-proof manner. By way of example, this would be of interest for conference rooms or for installations with increased security requirements.
On account of the properties of light, a line-of-sight (LoS) link is preferable for the light-based data transmission. Shadowing, caused by the human body, for example, and mobility, caused by the head being rotated, for example, represent a technical challenge that requires a suitable solution.
Multidirectional transceiver units are required in order to maintain a line-of-sight link in virtually any desired alignment of the body or of the device. Minimizing the number of components and the extent of wiring between the components helps reduce costs.
Current optical transceiver concepts operate according to a single input single output (SISO) principle on the part of the transmitter, for example. Here, a data signal to be transmitted is converted into an analog signal by means of a modulation method and converted into an analog power signal by a driver. Said analog power signal is converted into a light signal for optical wireless communication by an optoelectronic transmission element, for example a light-emitting diode (LED) or a laser diode (LD). This light signal is emitted by way of a suitable optical unit.
Additionally, solutions that operate according to a multiple input multiple output (MIMO) principle are also known. Here, for example on the transmitter side, the data signal is reshaped into an analog signal via a common modulator, supplied to a common driver and then distributed as an analog power signal to different optoelectronic transmission elements, each with a dedicated optical unit. In a corresponding manner, a light signal transmitted by the optical wireless link is captured on the receiver side by a plurality of different optoelectronic reception elements, each with a dedicated assigned optical unit, and combined into an analog electrical signal by way of a signal combining member which, in the simplest case, carries out equal gain combining (EGC), said electrical signal then being supplied to a common demodulator via an amplifier/filter device. Moreover, the drivers on the transmitter side or the amplifiers/filters on the receiver side can be weighted individually for the individual transmission paths or branches in order thereby to obtain better properties in view of the signal quality. By way of example, the signal levels of the individual transmission paths or branches can be weighted on the receiver side according to their signal-to-noise ratio (SNR) and subsequently be combined in order thereby to attain a signal with the best possible signal quality in relation to the SNR (maximum-ratio combining, MRC).
However, these solutions require a large number of components and consequently have great complexity. Distributing analog electrical signals, which by all means can have high-frequency signal components, is afflicted by losses and susceptible to interference in the process.